It is kinda like an exclamation of surprise or astonishment. In America you guys would say things like jee wiz or something. Sorry, I am not good with American slang.
My Dad says Crickey alot to. Whenever we visit he always says crikey this and crikey that.
I think I know what you mean about some of the things he says. But to me they sound normal, I don't really notice the words he uses. He does say "strewth" sometimes doesn't he? That means much the same as "crikey", it's just an exclamation.